An antiepileptic and mood stabiliser
Lamotrigine
A well-tolerated epilepsy medicine, also used to stabilise mood in bipolar disorder — introduced slowly because of the risk of a serious rash if started too fast.
What is Lamotrigine?
Lamotrigine is used to control several types of epileptic seizure and to prevent the low (depressive) episodes of bipolar disorder. It is generally well tolerated and does not cause the weight gain or sedation of some alternatives. The key safety point is that it must be started at a low amount and increased slowly, because starting too quickly raises the risk of a serious skin rash.
Education and reference only. This is a plain-language guide to Lamotrigine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Lamotrigine is a widely used antiepileptic medicine, effective across several seizure types, and it is also an established mood stabiliser in bipolar disorder — particularly good at preventing the depressive lows. It is often favoured because it is generally well tolerated, does not typically cause weight gain, sedation or cognitive dulling, and is considered one of the safer antiepileptics in pregnancy. It is taken as a daily tablet, and the way it is started — slowly — is central to using it safely.
How it works
Lamotrigine stabilises overactive nerve cells by blocking sodium channels they use to fire repeatedly, and it dampens the release of excitatory (stimulating) brain chemicals such as glutamate. This calms the excessive electrical activity that causes seizures. Its mood-stabilising effect in bipolar disorder is thought to come from these same calming actions on brain signalling, with a particular benefit in preventing depressive episodes.
What it treats
Conditions Lamotrigine is used for
Practical use
How to take Lamotrigine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it as prescribed, following the slow "start low, go slow" schedule exactly — do not rush the increases.
- Report any new skin rash promptly, especially in the first 8 weeks or with fever, blistering, or sore mouth/eyes.
- Do not stop suddenly — antiepileptics are reduced gradually to avoid seizures or mood destabilisation.
- Tell your prescriber if you take sodium valproate (a much slower schedule is needed) or start/stop hormonal contraception.
- Stick to the same brand or version where possible, as advised for epilepsy.
Weighing it up
Advantages & disadvantages of Lamotrigine
Advantages
- Effective for several seizure types and for preventing bipolar depression.
- Generally well tolerated — little weight gain, sedation or cognitive effect.
- Considered one of the safer antiepileptics in pregnancy, and does not reduce most contraception (though contraception can reduce its level).
Disadvantages
- Must be introduced slowly because of the risk of a serious rash.
- Levels are strongly affected by valproate and by hormonal contraception.
- Takes time to build to an effective amount.
Practical use
Good to know
The most important thing with lamotrigine is that it is introduced slowly, over several weeks, and the amount built up gradually — because starting too high or increasing too fast substantially raises the risk of a serious skin rash (which can rarely become severe, such as Stevens–Johnson syndrome). Report any new rash, especially in the first weeks or with fever, blistering or mouth/eye involvement, and seek prompt advice. Sodium valproate greatly raises lamotrigine levels, so a much slower, lower schedule is used when they are combined. Do not stop an antiepileptic suddenly. Some hormonal contraceptives can lower lamotrigine levels, so tell your prescriber if you start or stop them.
Who should not take it / use with caution
- People who have had a serious reaction to lamotrigine before.
- Used with care, and a modified schedule, in significant liver or kidney impairment and alongside valproate.
- Pregnancy and breastfeeding are managed individually — it is often continued as one of the preferred options, under specialist guidance; never stop suddenly.
Monitoring
- Seizure or mood control
- For skin rash, especially in the first weeks
- Dose review when interacting medicines (valproate, contraception) change
Side effects
- Common early on: skin rash (the reason for slow introduction), headache, dizziness, double vision, and nausea.
- Sometimes sleep disturbance, tremor or irritability.
- Rarely, a serious skin or hypersensitivity reaction (widespread rash with fever/blistering) or effects on the blood — seek urgent help for a spreading rash with feeling unwell.
Key interactions
- Sodium valproate substantially raises lamotrigine levels — a much slower, lower schedule is used, and the rash risk is higher.
- Enzyme-inducing antiepileptics (carbamazepine, phenytoin) and some hormonal contraceptives lower lamotrigine levels.
- Starting or stopping these, or the combined pill, can require a lamotrigine dose change.
Available as: Tablets, dispersible/chewable tablets that can be dissolved in water, for those who prefer them.
Answers
Lamotrigine: frequently asked questions
Why does lamotrigine have to be started so slowly?
Starting lamotrigine at too high an amount, or increasing it too quickly, raises the risk of a serious skin rash — occasionally a severe one. Introducing it slowly over several weeks greatly reduces this risk, which is why the schedule matters and should not be rushed.
What rash should I worry about?
Report any new rash while starting lamotrigine, particularly in the first 8 weeks. A widespread rash — especially with fever, blistering, or involvement of the mouth or eyes — can signal a rare but serious reaction: stop and seek urgent medical advice.
Why does taking valproate change my lamotrigine dose?
Sodium valproate slows the breakdown of lamotrigine, so its level rises and the rash risk increases. When the two are taken together, a much lower and slower lamotrigine schedule is used. Always make sure your prescriber knows you take both.
Is lamotrigine safe in pregnancy?
Lamotrigine is generally considered one of the preferred antiepileptics/mood stabilisers in pregnancy, but this is always an individual, specialist decision — and you should never stop an antiepileptic suddenly. If you are planning a pregnancy or become pregnant, speak to your specialist team, ideally in advance, as levels can change during pregnancy.
Authoritative sources
- BNF: Lamotrigine.
- electronic Medicines Compendium (SmPC): Lamotrigine (Lamictal).
- NICE NG217: Epilepsies; NG222/CG185: Bipolar disorder.
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